create and open function

create and open function

[Antoine JORGE RIBEIRO]

Hi!

I would like to know what is the meaning of the fourth paramtre in the
functions Create and Open from the packages Direct_IO, Sequential_IO or
Text_IO.

theses functions are described in Ada 95 Reference Manual :
(6)          procedure Create(File : in out File_Type;
                           Mode : in File_Mode := Out_File;
                           Name : in String := "";
                           Form : in String := "");
(7)          procedure Open  (File : in out File_Type;
                           Mode : in File_Mode;
                           Name : in String;
                           Form : in String := "");

if someone can explain it to me, that would be grate.
thanks

Antoine

Re: create and open function

[Markus Kuhn]

Antoine JORGE RIBEIRO wrote:
> I would like to know what is the meaning of the fourth paramtre in the
> functions Create and Open from the packages Direct_IO, Sequential_IO
> or Text_IO.
> 
> (6)          procedure Create(File : in out File_Type;
>                            Mode : in File_Mode := Out_File;
>                            Name : in String := "";
>                            Form : in String := "");

http://www.cl.cam.ac.uk/~mgk25/volatile/gnat_rm.html#SEC11

Markus

-- 
Markus G. Kuhn, Security Group, Computer Lab, Cambridge University, UK
email: mkuhn at acm.org,  home page: <http://www.cl.cam.ac.uk/~mgk25/>

Re: create and open function

[John Herro]

"Antoine JORGE RIBEIRO" <softst1@bruker.fr> writes:
> I would like to know what is the meaning
> of the fourth paramtre in the functions
> Create and Open from the packages
> Direct_IO, Sequential_IO or Text_IO.

     With some implementations of Ada, you can use the Form parameter to
specify how the file is implemented.  The null string specifies the default
options.
     Many implementations of Ada ignore the Form parameter completely.  If
there are any legal values for Form besides the null string, they will have to
be explained in the documentation that came with your compiler.  The meaning of
Form depends completely on the compiler that you are using.

- John Herro
You can download a shareware Ada Tutor program at
http://members.aol.com/AdaTutor

Re: create and open function

[dennison]

In article <901122614.215105@dedale.pandemonium.fr>,
  "Antoine JORGE RIBEIRO" <softst1@bruker.fr> wrote:
> I would like to know what is the meaning of the fourth paramtre in the
> functions Create and Open from the packages Direct_IO, Sequential_IO or
> Text_IO.
>
>                            Form : in String := "");

The meaning of that parameter is implementation-dependent. Quite often, it has
no meaning. Check with your compiler vendor docs to see.

On the Vax/Ada compiler you could stuff in RCS arguments like file
permissions, access control lists, and buffer sizes.

T.E.D.

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Re: create and open function

[Robert Dewar]

Antoine asks for the meaning of the form parameter

<<if someone can explain it to me, that would be grate.
thanks
>>

The answer is to look in the documentation from your vendor, since,
as the RM clearly indicates, the semantics of the form string is
implementation dependent.


In GNAT (as clearly described in the GNAT manuals), the form string is
used for specifying wide character encoding, and file sharing options,
among other items.